1. Field of the Invention
The present invention relates to the field of display technology, and more particularly, to a color display device structure and manufacturing method thereof.
2. Description of Related Art
The organic light emitting diode display (Organic Light Emitting Diode, OLED) is a very promising flat panel display technology, which not only has a very excellent display performance, but also has self-luminous, simple structure, ultra-thin, fast response, wide viewing angle, low power consumption, flexible display and other features, known as the “Dream monitor”. To be coupled with the investment of OLED in production equipment is much smaller than that of the liquid crystal display (Liquid Crystal Display, LCD), OLED has got the attention of the major display manufacturers and become the main force of third-generation display.
Currently, there are several color OLED technology roadmap. One is RGB (Red, Green, Blue, RGB) three-color light, Samsung company representative. This technique is only applicable to organic small molecules material easily sublimated. The advantage of the technology is mature, easy to operate. However, because of the need for high accuracy and precision of the mask alignment in the preparation of high-resolution display, it results in low productivity and high cost, and because of the life of the three primary colors, the excitation rate, and the large attenuation difference, it results in a color cast of the color display device.
The other is white +RGB filters (Color Filter, CF) technology to LG company representative. Since the CF technique of the LCD can be used, the mask alignment is not required, which greatly simplifies the vapor deposition process, and thus can reduce production cost and manufacture large-size high-resolution OLED. However, since most of the light energy is absorbed by the filter, only about 30% of the light is transmitted, so that the white light emitting material requires high performance, otherwise the efficiency of the display device is low, and is generally used for small molecule OLED display.
The third is that a blue OLED luminesce, through a green and red light color conversion method (Color conversion method, CCM) and the red and green light material excited by blue light, to obtain three primary colors, red, green and blue, achieving color display. Since the same production technology as that of the color filter can be used, it increases the pixel density, and can achieve a higher yield. But the blue material is the bottleneck restricting this technology. At this stage, it is generally only used for the preparation of small molecule OLED.
The semiconductor nanocrystals (semiconductor nanocrystals, NCs) has the size of 1-100 nm. Due to the size of the semiconductor nanocrystals smaller than the exciton Bohr radius of its material, that exhibits strong quantum confinement effect. The quasi-continuous energy band evolves into the discrete energy level structure similar to that of a molecule, showing a new material properties, also known as quantum dots (quantum dots, QDs).
Since the excitation of the external energy (photoluminescence, electroluminescence, cathodoluminescence, etc.), electrons are transited from the ground state to the excited state. The electrons and holes in the excited state may form excitons. The electrons and holes combine and ultimately relax to the ground state. The excess energy is released through the combination and relaxation processes, which may emit photons by radiative combination.
Quantum dots light emitting diode display (Quantum Dots Light Emitting Diode, QD-LED) has important commercial applications, arousing intense research interest in the last decade. Indeed, QD-LEDs have many advantages as compared with OLED: (1) because the line width of light emitted by the quantum dots is between 20-30 nm, relative to luminescence, longer than 50 nm, of OLED, the FWHM (Full Width at Half Maximum, FWHM) is narrow, which for color purity of the screen plays a key role; (2) the inorganic material with respect to the organic material exhibits a better thermal stability. When the device is in a high current density or high luminance, Joule heat is the main reason for degradation of the device. Because of the excellent thermal stability, the inorganic material-based devices will exhibit a long life; (3) since the lives of the different organic materials of red, green and blue color are different one another, the color of the OLED display will change over time. However, by using a material to synthesize the quantum dots of different sizes, due to the quantum confinement effect, the three primary colors light can be emitted. The same kind of material may exhibit a similar degradation of life; (4) QD-LED can emit infrared light, and the emission wavelength of an organic material is generally less than 1 micron; (5) there is no limitation to the spin statistics for quantum dots, and the external quantum efficiency (External Quantum Efficiency, EQE) may reach 100%.
QD-LED can be divided into organic-inorganic hybrid devices and full-inorganic devices. The former can achieve high brightness and flexible production. The latter has an advantage in terms of stability of the device. But reports of the QD-LED are relatively small, now.
It is therefore necessary to develop a new, simple production process to manufacture a thin color display device structures with high color purity, good emitting efficiency, and high stability.